Gonad
The gonads (from the Greek γονή [gonḗ], «generation») are the organs that generate gametes or sexual cells (the equivalent organs of plants are called gametangia). In vertebrates, they also perform a hormonal function, which is why they are also called sex glands.
Anatomy and Physiology
The female gonads are called ovaries, while the male gonads are called testicles or testes (singular, “teste”).
Some hermaphrodite animals have a single gonadal structure that produces both gametes, called ovotestis.
From a functional point of view, the reproductive organs can be classified as:
- Primary: those where gametogenesis and the secretion of sexual hormones take place. It's the case of ovary and testicles.
- Accessories: this consideration is given to the ducts through which the sperm comes out or the eggs are transported, as well as the glands that pour to the primary.
Embryology
In humans, the sexual glands only acquire male or female morphological characteristics in the seventh week of gestation. From the proliferation of the coelomic epithelium and condensation of the underlying mesenchyme, the genital or gonadal folds or ridges are formed. The germ cells or germ line only appear in the genital folds at week 6, and appear between the endodermal cells of the yolk sac and migrate along the dorsal mesentery reaching the primitive sex glands.
At the beginning of the 5th and 6th weeks, they invade the genital folds. In this way, the indifferent or bipotential sexual glands are formed, in which the coelomic epithelium of the genital fold proliferates and the epithelial cells penetrate the underlying mesenchyme.[citation needed]
The genes involved in the formation of the crest or urogenital fold and the migration of genital cells towards it to form a bipotential sex gland have been identified, the best known being SRY, which is located on the short arm of the Y chromosome and induces the bipotential sex gland to differentiate into a testis.
Hormonal only
The hormones that affect the gonads are generally related to spermatogenesis in men; As for women, the menstrual cycle, widely related to women, is regulated by hormones. All of these hormones come from the pituitary gland, more specifically, the anterior pituitary gland.
In the case of males, the hormones involved are FSH, LH and partly testosterone; in women the hormones are estrogen, progesterone, in addition to the gonadotropin hormones (LH and FSH).